This application is based on Application No. 2000-340220, filed in Japan on Nov. 8, 2000, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an automotive alternator.
2. Description of the Related Art
FIG. 17 is a cross section showing a construction of a conventional automotive alternator, FIG. 18 is a rear end elevation of the conventional automotive alternator, FIG. 19 is a perspective showing a rotor used in the conventional automotive alternator, and FIG. 20 is a perspective showing a stator used in the conventional automotive alternator.
In FIGS. 17 to 20, the conventional automotive alternator is constructed by rotatably mounting a Lundell-type rotor 7 by means of a shaft 6 inside a case 3 constructed from an aluminum front bracket 1 and an aluminum rear bracket 2, and fixing a stator 8 to an inner wall surface of the case 3 so as to cover an outer circumferential side of the rotor 7.
The shaft 6 is rotatably supported in the front bracket 1 and the rear bracket 2. A pulley 4 is fastened to a first end of this shaft 6 such that rotational torque from an engine can be transmitted to the shaft 6 by means of a belt (not shown).
Slip rings 9 for supplying electric current to the rotor 7 are fixed to a second end of the shaft 6, and a pair of brushes 10 are housed in a brush holder 11 disposed inside the case 3 such that the pair of brushes 10 slide in contact with the slip rings 9. A voltage regulator 18 for adjusting the magnitude of an alternating voltage generated in the stator 8 is fixed by adhesive to a regulator heat sink 17 fitted onto the brush holder 11. A rectifier 12 that is electrically connected to the stator 8 and converts alternating current generated in the stator 8 into direct current is mounted inside the case 3.
The rotor 7 is constituted by a rotor coil 13 for generating magnetic flux on passage of an electric current, and a pair of first and second pole cores 20 and 21 disposed so as to cover the rotor coil 13, magnetic poles being formed in the first and second pole cores 20 and 21 by magnetic flux generated in the rotor coil 13. The pair of first and second pole cores 20 and 21 are made of iron, each has a plurality of first and second claw-shaped magnetic poles 22 and 23 disposed on an outer circumferential perimeter at even pitch in a circumferential direction so as to project axially, and the first and second pole cores 20 and 21 are fixed to the shaft 6 facing each other such that the first and second claw-shaped magnetic poles 22 and 23 intermesh. In addition, centrifugal fans 5 are fixed to first and second axial ends of the rotor 7.
The stator 8 is constituted by a stator core 15, and a stator winding 16 formed by winding a conducting wire into this stator core 15, electric current being generated in the stator winding 16 by changes in the magnetic flux from the rotor 7 accompanying rotation of the rotor 7. The stator core 15 is formed into a cylindrical shape, and a plurality of slots 15a having grooves lying parallel to an axial direction are disposed at even angular pitch in a circumferential direction so as to open towards an inner circumferential side. The stator winding 16 is formed into a generally cylindrical shape by winding and stacking copper wires (conductor wires) having a circular cross section coated with electrical insulation into a wave shape, and is mounted to the stator core 15 by inserting the copper wires into each of the slots 15a from axially outside while bending a first coil end portion thereof towards an inner circumferential side.
Next, the construction of the rectifier 12 and the voltage regulator 18 will be explained with reference to FIGS. 22 to 28.
The brush holder 11 is made of an electrically-insulating resin, and is formed integrally with an annular shaft insertion portion 30, a circuit housing portion 31, a connector portion 32, and a mounting portion 33. An insert conductor group is insert molded into the brush holder 11, constituting wiring for component parts, also constituting connection terminals protruding out into the connector portion 32, and further constituting rectifier connection terminals 34, etc., functioning as electrical joint portions for the rectifier 12. The voltage regulator 18 is constructed by securing a voltage regulator circuit board (not shown) mounted with electronic components such as IC chips onto the regulator heat sink 17 using adhesive. The voltage regulator 18 is mounted in the circuit housing portion 31 by fitting the regulator heat sink 17 into the circuit housing portion 31 and sealing edge portions of the regulator heat sink 17 to the circuit housing portion 31. The voltage regulator circuit board of the voltage regulator 18 is housed inside the circuit housing portion 31 and sealed in using a resin. Brush holder mounting apertures 33a are disposed at first and second ends of the mounting portion 33.
The rectifier 12 is constituted by horseshoe-shaped first and second heat sinks 37 and 38 upon which are disposed first and second unidirectional conducting component packages 35 and 36, respectively, and a horseshoe-shaped rectifier circuit board 39. Each of the first unidirectional conducting component packages 35 is formed into a generally rectangular parallelepiped shape by molding a first diode 35a using a first electrically-insulating resin portion 35d, each of the first diodes 35a functioning as a semiconductor component constructed by joining an n-type semiconductor and a p-type semiconductor into a pn junction, a first heat-dissipating copper tab 35b being joined to the n-type semiconductor and a first diode connection terminal 35c being joined to the p-type semiconductor. Each of the second unidirectional conducting component packages 36 is formed into a generally rectangular parallelepiped shape by molding a second diode 36a using a second electrically-insulating resin portion 36d, each of the second diodes 36a functioning as a semiconductor component constructed by joining an n-type semiconductor and a p-type semiconductor into a pn junction, a second heat-dissipating copper tab 36b being joined to the p-type semiconductor and a second diode connection terminal 36c being joined to the n-type semiconductor. Eight first unidirectional conducting component packages 35 are arranged in a circumferential direction with the first heat-dissipating copper tabs 35b joined to a main surface of the first heat sink 37, and a plurality of heat-dissipating fins 37a are disposed in a radial pattern on a rear surface of the first heat sink 37. Similarly, eight second unidirectional conducting component packages 36 are arranged in a circumferential direction with the second heat-dissipating copper tabs 36b joined to a main surface of the second heat sink 38. In the rectifier circuit board 39, an insert conductor group is formed by insert molding and constitutes first rectifier circuit board connection terminals 39b functioning as electrical joint portions for the first and second diode connection terminals 35c and 36c of the first and second unidirectional conducting component packages 35 and 36 and second rectifier circuit board connection terminals 39c functioning as electrical joint portions for the voltage regulator 18. In addition, rectifier circuit board mounting apertures 39a are disposed at first and second end portions and a central portion of the rectifier circuit board 39. Moreover, one of the rectifier circuit board mounting apertures 39a is used as an output terminal for the rectifier 12.
The rectifier 12 is constructed by disposing the first and second rectifier heat sinks 37 and 38 coaxially such that main surfaces thereof are positioned in a common plane, disposing the rectifier circuit board 39 on the main surfaces of the first and second rectifier heat sinks 37 and 38, and joining the first and second diode connection terminals 35c and 36c of the first and second unidirectional conducting component packages 35 and 36 to the first rectifier circuit board connection terminals 39b of the rectifier circuit board 39. Electrical insulation of the first and second rectifier heat sinks 37 and 38 is ensured by electrically-insulating bushes 40.
Here, the brush holder 11 is secured to an inner wall surface of the rear bracket 2 by mounting screws (not shown) that pass through the brush holder mounting apertures 33a of the brush holder mounting portion 33, and the rectifier 12 is secured to an inner wall surface of the rear bracket 2 by mounting screws (not shown) that pass through the rectifier circuit board mounting apertures 39a. The brush holder 11 and the rectifier 12 are disposed in an annular shape surrounding the shaft 6. Thus, the second heat-dissipating copper tabs 36b of the second unidirectional conducting component packages 36 of the rectifier 12 are electrically connected to the rear bracket 2 through the second heat sink 38 and grounded.
The voltage regulator 18 and the rectifier 12 are electrically connected by the connection of the rectifier assembly connection terminals 34 and the second rectifier circuit board connection terminals 39c. Output wires and neutral point lead wires of the stator winding 16 are each connected to the second rectifier circuit board connection terminals 39b of the rectifier circuit board 39, constituting the circuit shown in FIG. 21. Moreover, the rectifier 12 is constituted by first and second rectifier sets 12a and 12b, each including a bridge circuit constituted by four first unidirectional conducting component packages 35 (first diodes 35a) and four second unidirectional conducting component packages 36 (second diodes 36a). Thus, the alternating-current outputs of first and second three-phase alternating-current windings 16a and 16b constituting the stator winding 16 undergo three-phase full-wave rectification by the first and second rectifier sets 12a and 12b, respectively, and are then combined. Because ripple currents flowing through the neutral points of the first and second three-phase alternating-current windings 16a and 16b are picked up, output is improved.
In a conventional automotive alternator constructed in this manner, an electric current is supplied from a battery (not shown) through the brushes 10 and the slip rings 9 to the rotor coil 13, generating a magnetic flux. The first claw-shaped magnetic poles 22 on the first pole core 20 are magnetized into North-seeking (N) poles by this magnetic flux, and the second claw-shaped magnetic poles 23 on the second pole core 21 are magnetized into South-seeking (S) poles. Rotational torque from the engine is transmitted to the shaft 6 through the belt and the pulley 4, rotating the rotor 7. Thus a rotating magnetic field is imparted to the stator winding 16, generating an electromotive force in the stator winding 16. This alternating-current electromotive force passes through the rectifier 12 where it is converted into direct current and the magnitude thereof is regulated by the voltage regulator 18, charging the battery.
Now, the rotor coil 13, the stator winding 16, the rectifier 12, and the voltage regulator 18 continuously generate heat during power generation, and in an alternator having a rated output current in the 100A class, they generate heat of 60W, 500W, 120W, and 6W, respectively, at a rotational speed showing high temperature.
Thus, in order to cool the heat generated by power generation, front-end and rear-end air intake apertures 1a and 2a and front-end and rear-end air discharge apertures 1b and 2b are disposed in the front bracket 1 and the rear bracket 2.
At the rear end, external air is sucked in through the rear-end air intake apertures 2a disposed facing the first rectifier heat sink 37 of the rectifier 12 and the regulator heat sink 17 of the voltage regulator 18, respectively, due to the rotation of the centrifugal fans 5, then flows radially inwards along the heat-dissipating fins of the first rectifier heat sink 37 and the regulator heat sink 17 to an inner circumferential edge of the first rectifier heat sink 37 and the regulator heat sink 17, next flows in an axial direction to the rotor 7, and is then deflected centrifugally by the centrifugal fans 5, cooling a rear-end coil end group 16r of the stator winding 16 before being expelled to the outside through the rear-end air discharge apertures 2b. At this time, the heat generated in the first unidirectional conducting component packages 35 is transferred from the first heat-dissipating copper tabs 35b to the first rectifier heat sink 37 and is dissipated from the heat-dissipating fins 37a. The heat generated in the second unidirectional conducting component packages 36 is transferred from the second heat-dissipating copper tabs 36b to the rear bracket 2 and is dissipated from the rear bracket 2. In addition, the heat generated in the voltage regulator 18 is transferred to the regulator heat sink 17 and dissipated by heat-dissipating fins of the regulator heat sink 17.
At the same time, at the front end, external air is sucked in axially through the front-end air intake apertures 1a due to the rotation of the centrifugal fans 5, and is then deflected centrifugally by the centrifugal fans 5, cooling a front-end coil end group 16f of the stator winding 16 before being expelled to the outside through the front-end air discharge apertures 1b. 
In this conventional automotive alternator, as explained above, the voltage regulator 18 is mounted in the circuit housing portion 31 of the brush holder 11, the brush holder 11 is mounted to the rear bracket 2 using the brush holder mounting portion 33, and at the same time the rectifier 12 is mounted to the rear bracket 2 using the rectifier circuit board 39. Thus, in the conventional automotive alternator, because the voltage regulator 18 and the rectifier 12 each require their own separate supporting members, one problem has been that the number of parts is large, making assembly poor.
The present invention aims to solve the above problems and an object of the present invention is to provide an automotive alternator enabling improved assembly by mounting a rectifier and a voltage regulator on a bracket supported by a single supporting member to reduce the number of parts.
In order to achieve the above object, according to one aspect of the present invention, there is provided an automotive alternator including:
a shaft rotatably supported by a bracket;
a rotor fastened to the shaft, the rotor being disposed inside the bracket;
a stator fastened to the bracket so as to envelop an outer circumference of the rotor;
a rectifier for rectifying an alternating-current output of the stator, the rectifier being provided with a rectifier heat sink on which a plurality of semiconductor components is disposed and a rectifier circuit board for connecting the plurality of semiconductor components so as to constitute a bridge circuit;
a voltage regulator for adjusting an output voltage of the rectifier, the voltage regulator being provided with a voltage regulator circuit board on which a voltage regulating circuit is formed and a voltage regulator heat sink on which the voltage regulator circuit board is disposed; and
a cooling means for cooling the rectifier and the voltage regulator,
wherein the plurality of semiconductor components and the voltage regulator circuit board are supported by a single supporting member and mounted to the bracket.
The supporting member may be constructed by integrating the rectifier heat sink and the voltage regulator heat sink.
The rectifier heat sink and the voltage regulator heat sink may be integrated by interposing a linking member, the linking member being composed of a material having a coefficient of thermal conductivity less than coefficients of thermal conductivity of the rectifier heat sink and the voltage regulator heat sink.
The cooling means may be a centrifugal fan disposed inside the bracket, and the supporting member may be formed into an annular shape and mounted to the bracket so as to be perpendicular to an axis of the shaft, the plurality of semiconductor components and the voltage regulator circuit board being distributed in a circumferential direction around the shaft.
The cooling means may be constituted by a conduit disposed in the bracket and a coolant distributed through the conduit.
The semiconductor components may be constituted by MOSFETs.
The stator may include a cylindrical stator core in which slots extending axially are disposed at a predetermined pitch in a circumferential direction, and a stator winding formed by installing conductor wires, each conductor wire being folded over outside the slots at an end surface of the stator core so as to occupy different layers in a slot depth direction in the slots at predetermined slot intervals, wherein folded-over portions of the conductor wires constitute coil ends, and a coil end group of the stator winding is constituted by arranging the coil ends in neat rows in a circumferential direction.